Apparatus for correcting the course on board aeroplanes



' Aug. 18, 1925. 1,550,174

Y. P. G. LE PRIEUR API ARATUS FOR CORRECTING THE-COURSE ON BOARD AEROPLANES Filed June 6, 1921 4 Sheets-Shet l Aug. 18, 1925. 1,550,174

Y. P. G. LE PRIEUR APPARATUS FOR CORRECTING THE .COURSE ON BOARD AEROPLANES Filed June 1921 4 Sheets-Sheet 2 M2 10/ H923. TM I A fl y.4.

Aug. 18, 1925. 1,550,174

Y. P. G.LE PRIEUR I APPARATUS FOR CORRECTING THE COURSE ON BOARD AEROPLANES GZcZaie H1 1 J mm? Aug. 18, 1925. 1,550,174

Y. G. LE PRIEUR APPARATUS FOR CORRECTING THE COURSE ON BOARD AEROPLANES Filed June 6, 1921 4 Sheets-S heet 4 Figa l3.

l l 1 l l l l Patented Au 18, 1925.

YVES PAUL GASTON LE PRIEUR, or PARIS, FRANCE.

APPARATUS FOR CORRECTING THE oounsr: ON BOARD AEROPLANES.

, Application filed June 6,1921. Serial No. 475,489.

(en-ANTED UNTER THE raovrsrons or THE AcT or MARCH 3, 1921, 41 STAT. 1. 1318.)

T 0 all whom it may concern:

Be it known that I, Yvns PAUL GAs'roN Ln PRIEUR, a citizen of the French Republic, residing at 61 Rue Pernety, Paris, France, have invented certain new and useful Ap paratus for Correcting the Course on Board Aeroplanes (for which I have filed an application for patent in France on June 5, 1921, No'. 517,904), of which the following is a specification. v 1 ,1 When a pilot is engaged in making preparations to travel with'an aeroplane from one point to another, he draws upon the map a straight line connecting the two points and then measures the direction of this line. Should there be no wind prevailing at the time, it-would be sufficient to maintain the aeroplane upon this course as indicated by the compass, this latter being corrected for any inherent errors if required. But in practice theaction of the wind constitutes a very appreciable influence in modifying the course followed by the aeroplane, thus introducing a factor of uncertainty into the estimate of the position of the aeroplane, and this becomes still moreconsiderable when the speed and direction of the wind are subject to frequent changes. Fora given speed of the wind, the actual speed of the aeroplane with reference to the ground is both in magnitude and direction the resultant of the air speed of the aeroplane in calm air and the speed of the wind.

These three speeds form a triangle, and the angle made by the center line of the areoplane with the route followed along the ground is termed the angle of drift. Should it be desired to obtain a correct course, the pilot may be enabled to determine the compass point to be usedfor steering at each instant whereby this result may be obtained, he is consequently required to know the speed of the wind. This speed may be deduced, as will be set forth hereunder, from the measurement of the angle of drift which is made by the pilot during the travel of the aeroplane by observing the direction of move ment of visiblepoints on the ground with reference to the center line of the aeroplane.

The path rectifying apparatus according to my invention permits determining the speed of the wind'by causing the aeroplane to successively follow two courses on different points of the compass, and in measuring the angle of drift corresponding to each of the said courses. v

The accompanying drawings show by way of example, various constructional forms of my correcting apparatus.

In the drawings:

Figure l is a. plan view of the correcting apparatus with a drift meter on the gyroscope principle.

Fig. 2 is a longitudinal section in elevation of the said gyroscope drift meter on the line X-X of Fig. 1.

Fig. 3 is a diagrammatic view illustrating I the graphic method for measuring the drift.

Fig. 4: is a graphic diagram of an observa tion as obtained upon the board. i

Fig. 5 shows in perspective the first constructional form of the recordingdevice comprising an articulated parallelogram.

Fig. 6 is, a diagrammatic view illustrating the operation of the same.

Fig. 7 showsthe use of the graphic diagram obtained by the said drift-meter in the apparatus shown in Fig. 1.

Fig. 8 is. a diagrammatic view showing a second constructional form of the graphic diagram apparatus constituted by a camera.

Fig. 9 is a diagrammatic view illnstrating the graphic method in the case where the observations are transferred to a vertical board.

Fig. 10 represents the latter board with.

the diagram of an observation.

F igs. 1,1 and 12 show in perspective two graphic diagram devices, whereof one is provided with an articulated parallellogram and the other with a camera, for the use of the said vertical diagram;

Fig. 13 is a view of the assembled route rectifier installed in the keel of an aeroplane.

The path rectifying apparatus (Fig. 1) comprises a small board 1 disposed before the observer and having mounted thereon the toothed disk 2 which is revoluble about its shaft 3. The disk 2 carries a graduated scale which is the same as the compass scale. The said disk is provided With a plane table 4 whereon may be secured a sheet of paper 5 by means of the hoop 6 which is adapted to fit upon the edges of the paper in order to maintain the same. The sheet or chart 5 carries a set of parallel lines. The plane table 4 carriesthe reference line 7, and the ruled chart is so disposed that its lines shall be parallel to this line 7. The toothed disk 2 rotates before a stationary pointer 8 which is situated upon the center line of the aero- 'board 13 and in front of the pointer 14.

This latter disk is disposed before the pilot and beside the steering compass. At the point 15 of the boar-d 1 and in the same longitudinal plane as thecenter 3 and the pointer 8 at a distance from the center representing the speed of the airplane in calm air, is pivoted the apparatus known as drift-meter upon a vertical axis, this being a sighting apparatus operating according to a vertical sighting plane 17. The ruler 18, which is secured to the said driftmeter 16, is disposed parallel to the sighting plane and the inner edge thereof is caused to pass through the point 15, the ruler thus moving over the chart 5 to correspond wit the movements of the drift-meter.

' This apparatus is employed in the following manner If it is supposed that the geographical course to be followed is for instance due north, the aeroplane will start out on its course according to the north point of the compass; should it be submitted to the action of a wind having the speed V, it will follo-win reality another route with reference to the ground. The chart 5 is disposed upon the plane table 4 in such manner that its set of parallel lines shall be situated in the direction of the reference line 7, and the plane table 4 has been so disposed upon the graduated disk 2 that its reference line 7 shall be located opposite the graduation corresponding to the geographical course to be followed, or the north in the present case.

The graduated disk 2, which is used by the observer in order-to transmit his indications for the route to the pilot by meansof the repeating disk 11, is constantly di-' rected in the same manner as a compass card if the pilot controls correctly-by following the graduations of the repeating disk, that is, the chart 5 is always properly directed in space, the reference line 7 and the set of parallel lines being directed towards the geographical north.

lVhile the aeroplane is holding the actual course (Fig. 4) the observer measures an angle of drift (1 by so'disposing the ruler 18 that a chosen visible point on the-ground shall be seen to pass along the sighting plane 17 of the drift-meter 16. He then draws a bus Y upon the chart, whereupon he directs the course on a compass line which is quite different from the first one, for example N. 60 bringing the corresponding divisionof the graduated disk 2 opposite the pointer 8, thus transmitting the necessary indication to the pilot.

He thereupon makes a second measurement of an angle of drift (1' and uses the ruler'18 to draw upon the chart 5 the, line Y. -The two lines Y and Y will intersect at a point 19 which gives the extremity of the line representing thespeed of the wind AB to the same. scale upon which the air speed of the aeroplane is represented by the distance from the center 3 to the pivot 15 of the drift-meter.

. To, determine the course according to the compass which is to be employed for the aeroplane in order that it shall be made to follow the actual direction along the ground, that is, due north, the worm 9 is operated in order to bring the reference line 7 of the plane table and the set of lines of the chart 5 parallel to the ruler 18 at the same time that the said ruler shall pass through the point 19, this being the position shown in Fig. 1. The compass point of the course to be followed is now the one which is indi-' cated by the division of the graduated circle much as this division is reproduced by the disk 11 opposite the pointer 14, the pilot will therefore steer the aeroplane according 'to' the new course which is indicated. This compass will cause the aeroplane to follow along the ground-or the route due north, which is the correct route to be followed. The angle of drift for this route is the angle made by the ruler 18 in the position shown in Fig. 1 with reference to the center line of the aeroplane. The observer verifies from time to time that the drift-meter when in this position will in fact correspond to the actual drift, and should he note any appreciable change in the drift, he will make new measurements by the method above indicated in order to determine the new course to be followed according to the compass such as enable him to return to the veritable and correct route under the new conditions of the wind.

The drift-meter which is shown in Fig. 2 comprises a casing 2O provided in the interior with a .pivot 21 having revoluble thereon a gyroscope disk 22 of the known type which has theproperty of maintaining its axis in the vertical position irrespectively of the inclination and other movements of its support. The rotation of 7 said luminous line.

is adapted to produce a vacuum within the casing 20; The gyroscope 22 has mounted thereon a collimator 24 com rising a lens 25 and-a slit 26 disposed at't e focus thereof and forming an optical system whose axis is perpendicular to the axis of the gyroscope and is therefore invariably in the the rotation of' the gyroscope. The lighting is obtained by horizontal position durin a lamp 27 situated atthe focus ofa lens 28 which is disposed within the casing 20. On the opposite side of the said casing and rearwardly of the aperture 29 1s disposed a pentagonal prism 30 which 1s secured in the casing 20, the said prism being of the known type wherein the rays entermg at the face 31 are submitted to two total reflections and pass out through the face 32 in a direction exactly perpendicular to thelr original direction.

The operation of the sald drift-meter 1s as follows: When the gyroscope is in rotation its axis will remain in the vertical position, and the rays passing through the collimator 24.will form an image of the slit 26 in a plane which is invariably horizontal. The light beam passing through the aperture 29 will form outwardly of the pentagonal prism 30 the image of the sl1t at an infinite distance, and whose vertical position remains unaffected by jarring movements or the pitching or rolling of the aeroplane. path of the beam will perceive a luminous line which is in an absolutely fixed posltion and appears projected upon the ground, this latter being also observed by the other eye by direct vision. Under these conditions, it is an easy matter to so direct the drift-meter that a given visible point onthe ground shall be seen to pass along 1n the vertical plane of sighting and along the This disposition enables the measurement of the angle of drift to be carried out in a very easy and exact manner, provided the aeroplane has no zigzarr or yawing motion. I The ruler 18' is provided with a scale graduation in speeds, the length 153, or O A being taken as unity. The'point on the said ruler upon which is projected the point of intersection 19 of. the two llnes Y Y' indicates the speed'with reference to the ground, taking as unity the air speed of the aeroplane in calm air, that is, it indicates the coeflicient by which the latter, which is a known quantity, is to be multi plied in order to obtain the former.

The graphic method used for the meas urement of an angle of drift as well as the corresponding apparatus are set forth as follows:

Considering as in Fig. 3 an aeroplane 101 having an air speed represented by the arrow 102 and traveling in reality at the The eye placed at 33 in they speed represented by the arrow 103 by reason of the action of the wind; tracing upon the ground 104 the .line 105 constituting the projection of the line of travel of the aeroplane, this line will represent the actual course of'the aeroplane with reference to the ground. The movement of the aeroplane with reference to the ground is the 108.? line 109 which is parallel to the actual route of the aeroplane with reference to the ground. Whatever may be the point chosen, provided the compass course of the aeroplane and the wind remain unchanged, the records of all the sighting operations on different points of the ground which are made upon the board 108 will be parallel lines. The angle made by these lines with the centre line of the aeroplane represented by arrow 102 will constitute the angle 0 r1 But as a matter of fact, the aeroplane will I not preserve an invariable direction in space by reason of the difliculty encountered in following the course according to the compass, and it is furthermore submitted to pitching and rolling motion whereby the successivelines of sighting on a given point will-n0 longer be located in the same plane, but will more or less depart therefrom. by reason of such accidental movemen s. For this reason the ing line of the point 106 upon the observation board 108 will no longer be a straight line, but an irregular undulated line 110 as shown in Fig. 4. But this undulated line will have a well-determined general direc- 1 ion 111 which may be readily marked out and will be exactly parallel to the actual line 'of speed of the aeroplane with reference to the ground. This graphic method of measuring the angle of drift will eliminate the accidental errors by giving the mean of a considerable number of observations.

In the first constructional form of apparatus for the application of this graphic method as shown in Fig. 5, the apparatus is mounted upon the support or base 112 perpendicular to the board 108 which as stated is disposed horizontally in the aeroplane when in normal position of flight. The upright112 has disposed thereon a horizontal tube 113 having pivoted thereto the lower path 109 of the sight-" ill] ' the mean direction of the lines of the chart member of an articulated parallelogram, the sides whereof are provided respectively at 115 with a sighting device and at 116 with the pencil 117-adapted to bear upon the paper or chart of the board 108. By reason of this disposition, the two opposite sides 115 and 116 will remain invariably parallel, and the line of sight 115 is. susceptible of assuming all required positions in space for the purpose of sighting and following any desired point. Should this sighting line 15 (Fig. 6) be used to follow the movements of a given point on the ground, the pencil 117 Wlll draw upon the chart 108 a line 111 corresponding to the line 111' representing the movement of the said pointon the ground with reference to the aeroplane, and by observing various'points the result will be a set of lines such as 108".

This latter set of lines is used in the device hereinbefore described and shown in Fig. 1, as indicated in Fig. 7. The board 1.08 may be given a displacement; perpendicular to the center line of the aeroplane whereby it shall be caused to pass from the position of observation below the pencil 117 Fig. 6 to the position of useFig. 7. As hereinbefore set forth, the course-correcting device 120 is provided with a ruler 121 for producing the required geometrical plan. The said ruler is provided with an extension arm 122 movable over the sheet of paper 108, and the said arm is to be directed according to the measured angle of drift; for this purpose it is made to coincide with In Fig. 8 is shown a second constructional i form of device for producing the driftmeter chart, which comprises a camera 123 provided with a lens or an aperture 124 and screen which is horizontal under normal conditions of flight. A point on the ground 126 will produce its image at 126', and when its relative movement brings it to the point 127, the image will now have moved to the point 127 By inscribingupon the screen 125 all the positions of this image, the result will be a sinuous line similar to the lines shown in Fig. 4.

The observation diagram may likewise be made upon a vertical board disposed perpendicular to the'center line of the aero plane, and in this .case the operation is represented diagrammatically in Fig. 9.

. The aeroplane 1228 moves above the ground parallel to 130, the image of this point 131 moves upon the board 132 according to a straight line which passes through the vanishing point 133 of the direction line 130.

This vanishing point is determined as is All that is necessary is to take the intersection of the line drawn upon the board 132 during the sighting operation with the horizon line 134, in order to obtain the van ishing point 133 and to be enabled to draw the line 128-133 from the vanishing point and to measure the angle between this line and the center line of the aeroplane, that is the angle of drift.

By making successive observations of a certain number of points 131-135, Fig. 9, this will produce various lines upon the board 132, and all of the said lines should intersect the horizon line 134 at the same point. In this manner a mean position may be taken if the concordance is not exact.'

This method of observation upon a vertical board may be used when the points on the ground situated below the aeroplane are not visible for any reason, for instance in the presence of clouds, but where the horizon is clear and may be thus observed. As concerns the efi'ect of the accidental movements of the aeroplane upon the observation diagram, the same indications will hold good which have been herein set forth in the case the diagram formed upon the horizontal board, and the result will be as shown in Fig. 10. A certain number of sinuous lines 136 will thus'beobtained upon the board 132 whose mean direction line will coincide in the vanishing point 133 located on the horizon line 134. The distance from this point 133 to the longitudinal plane of the aeroplane passing through the observation point and Whose record is shown at 137 will afiord the measurement of the angle of drift. The vertical board 132 may be disposed either forwardly or rearwa'rdly of the observer. In the former case the successive points of a given observation will descend longitudinal plane of the aeroplane, an ar ticulated parallelogram whose upper arm 140 is provided with a sighting device and whose lower arm is provided with a pencil 142. Upon the board 132 are drawn the rec ords of observations as shown by the sinuous lines 136, and the mean directions of the same will intersect at the vanishing point 133 located on the horizon line 134. The movement which is made in order' to bring the point. of the pencil to 133 will effect a parallel movement of the ruler 121 and this latter will be thereby directed according to the angle of drift, in such manner that the desired geometrical diagrams may immediately be produced.

In the apparatus shown in Fig. 12 the diagram is formed upon a vertical screen constituting the rear portion of a camera 14A. When the vanishing point 133 has been obtained as before, the ruler 120 is brought upon the bottom of the vertical line-passing through this point 133 in order to carry out the desired geometrical constructions. The board which is disposed upon the aeroplane for drawing the lines corresponding to the sighting operations may be given another direction than the vertical or horizontal, and the angle of drift may be ascertained in all such positions; however, this operation is particularly simple in the two cases herein mentioned.

Fig. 13 shows the assembled route rectifier, installed in the nacelle of an aeroplane. 150 designates the compass and 151 the body of the aeroplane. The route rectifying ap paratus is placed in front of the seat of the observer 153 and. the order transmitting disk 13 is placed in front of the seat of the pilot 1541. 152 is an openingprovided in the bottom of the nacelle to permit the ground to be observed by means of the sighting member 115.

Having now particularly described and ascertained the nature of my said invention and in what manner the same is to be performed, I declare that whatI claim is:

1. The combination with an aeroplane and -a compass on said aeroplane, of

an aeroplane path rectifying device comprising a fixed horizontal board, a graduated disk rotatable on said board and having graduations identical with graduations of the compass, means to direct said disk like the compass, a sighting device carried by the said board, a rule pivoted on a vertical axis located in the same longitudinal plane of the aeroplane as the center of board, a rule pivoted on a vertical axis located in the same longitudinal plane of the aeroplane as the center of the above disk and at a distance from the center representing the air speed of the aeroplane, a sighting device carried by the said board, a sighting inscription member combined with the said sighting device for tracing on a horizontal plate lines substantially parallel to the sighting plane, and means to direct the rule along the said lines.

3. The combination with an aeroplane and a compass on said aeroplane, of anaeroplane path rectifying device comprising a fixed horizontal board, a graduated disk rotatable on said board and having graduations identical with graduations of the compass, means to direct said disk like the compass, a sheet marked with parallel lines on said disk, a second disk repeating the movement of the said disk, a vertical column supporting a horizontal sleeve, a pivoted parallelogram whose lower side is engaged in said horizontal sleeve, a sight line on one of the small sides of the parallelogram and an inscribing stylus on the opposite side, a horizontal plate movable perpendicular to the axis of the aeroplane and adapted to be first placed under the stylus opposite the rotatable disk and a horizontal rule pivoted on a vertical axis located in the same longitudinal plane of the aeroplane as the center of the rotatable disk and at a distance from the center representing the air speed of the aeroplane and provided with an extension below which the above said plate is placed.

In witness whereof I have hereunto set my hand.

YVES PAUL GASTON LE PRIEUR. 

